1. Field of the Invention
The present invention relates to a radiographic image capturing apparatus for compressing a target object to be examined of an examinee, irradiating the target object with radiation, and then detecting and converting radiation that has passed through the target object into a radiographic image.
2. Description of the Related Art
Heretofore, a biopsy procedure has widely been performed in which a sampling needle is inserted into a target object to be examined in order to extract a tissue sample from a test region in the target object. More specifically, a biopsy apparatus for carrying out such a biopsy procedure is incorporated in a radiographic image capturing apparatus for capturing radiographic images of target objects to be examined. The radiographic image capturing apparatus, with the biopsy apparatus incorporated therein, operates in the following manner. A target object to be examined, such as the breast of a patient or a phantom that simulates a breast, is placed on an image capturing base (holding member) and is compressed by a compression plate (compression member), and then the target object is irradiated with radiation. Radiation that has passed through the target object is converted into a radiographic image by a radiation detector. Based on the position of a test region in the target object, which is obtained from the radiographic image, a sampling needle is inserted into the target object to remove a sample tissue of the test region.
Two processes are available in the art for inserting a sampling needle into a target object. According to one of the processes, which may be referred to as a vertical approach process, the sampling needle is inserted through an opening in the compression plate into the target object, along a direction in which the target object is compressed by the compression plate, i.e., along a direction toward the holding member. The other process, which may be referred to as a lateral approach process, inserts the sampling needle laterally into a side area of the target object, which is compressed by the compression plate.
According to the lateral approach process, in a case where the target object is viewed in front elevation, the sampling needle pierces a side area of the target object along a horizontal direction thereof. Therefore, the compression plate does not need to have an opening therein for allowing the sampling needle to pass therethrough. However, since the target object is compressed under uniform pressure along the horizontal direction, in a case where the sampling needle is inserted into the side area of the target object perpendicularly to the direction in which the target object is compressed, the target object is likely to become positionally displaced in a direction away from the side area that is pierced by the sampling needle.
According to the lateral approach process, therefore, compared to the vertical approach process, the pressure applied to compress the target object tends to be stronger, so as to prevent the target object from being unduly positionally displaced. Such increased pressure, which is applied to the target object, poses a greater burden on the target object.
Japanese Laid-Open Patent Publication No. 2009-207681 and U.S. Patent Application Publication No. 2009/0135997 disclose methods of compressing a target object. According to the compressing method disclosed in Japanese Laid-Open Patent Publication No. 2009-207681, a compression plate is tilted along a depth-wise direction of the target object to compress and hold the target object obliquely to the depth-wise direction. The compressing method disclosed in U.S. Patent Application Publication No. 2009/0135997 uses two rods that extend in a depth-wise direction of the target object. The two rods support respective opposite ends of a flexible sheet and are displaced toward the image capturing base until they reach the same height, whereupon the target object held on the image capturing base is covered with the sheet.